Difference between revisions of "Underworld"

Revision as of 06:52, 8 September 2016

The underworld refers to all indoor locations; including dungeons, caves, and houses.

Important Hex Addresses

Room Data

Room Headers

$027502-$027781 - Pointer Table, 2 byte local addresses, indexed by room ID.
$027781-$027FEF - Data

Headers are $0E (Decimal: 14) bytes formatted thusly:

byte 0: aaab bbcd
the a bits are transformed into 0000 0aaa and stored to $0414 ("BG2" in Hyrule Magic)

the b bits are transformed into 0000 0bbb and stored to $046C ("Collision" in Hyrule Magic)

the c bit is unused

the d bit is stored to $7EC005 (If set, use a lights out routine in the room transition)

byte 1: aabb bbbb
the a bits are unused

the b bits are transformed into bbbb bb00, thus making them a multiple of 4.

This value is used to load 4 different palettes for the dungeon, and corresponds to, you guessed it, Palette # in Hyrule Magic!
The resulting index is used to load values for $0AB6, $0AAC, $0AAD, and $0AAE

byte 2: gets stored to $0AA2 (GFX # in Hyrule Magic)

byte 3: value + #$40 gets stored to $0AA3 (Sprite GFX # in Hyrule Magic)

byte 4: gets stored to $00AD ("Effect" in Hyrule Magic)

byte 5: gets stored to $00AE ("Tag1" in Hyrule Magic)

byte 6: gets stored to $00AF ("Tag2" in Hyrule Magic)

These are the planes to use for bytes 9 through D. This determines which BG you appear on, and possibly more.

byte 7: aabb ccdd
the a bits are transformed into 0000 00aa and stored to $063F

the b bits are transformed into 0000 00bb and stored to $063E

the c bits are transformed into 0000 00cc and stored to $063D

the d bits are transformed into 0000 00dd and stored to $063C

Note, the only safe values for a plane seem to be 0,1, or 2. Hyrule Magic appears to violate this rule by letting you put 3 down, but nothing higher.

byte 8: aaaa aabb
the a bits are unused

the b bits are transformed into 0000 00bb and stored to $0640

byte 9: stored to $7EC000 These are all room numbers that you could possibly exit to.

byte A: stored to $7EC001

byte B: stored to $7EC002

byte C: stored to $7EC003

byte D: stored to $7EC004

Sprite Data

$04D62E-$04D92E - Pointer Table, 2 byte local addresses, indexed by room.
$04D92E-$04EC9D - Data

Sprite data is formatted thusly:

First Byte: Stored to $0FB3. Not sure what the purpose of that is yet.

After the first byte, you will see 3 byte clusters that break down thus:

First Byte:
Bits 4,3,2,1,0 - Y coordinate (in pixels from the top, starting at 0) of the sprite divided by 16.

Bits 6,5 - If these are set, they will be used to generate a subtype, stored to $0E30, X.

Bit 7 - If set, the sprite is on BG2, if not it's on BG1

Second Byte:
Bits 4,3,2,1,0 - X coordinate (in pixels from the far left, starting at 0) of the sprite divided by 16.

Bits 7,6,5 - If all these bits are set then this is an Overlord, otherwise it's a normal sprite. If only some of them are set they can be used to generate a subtype, stored at $0E30, X

Third Byte: Sprite or Overlord type. If a sprite, this will get loaded into a slot at $0E20, X. If an Overlord, will get loaded to $0B00, X.

The array is terminated with a byte of $FF.

Object Data

$0F8000-$0F83BF - Pointer Table, 3 byte long addresses, indexed by room ID.

Byte layout:

byte0: aaaa bbbb.
The a bits are transformed to aaaa0000 and select the type of empty space to fill in. Hyrule Magic calls this 'Floor 1' - Gets stored to $7E0490

The b bits are transformed to bbbb0000 and are the what Hyrule Magic calls 'Floor 2' - Gets stored to $7E046A

byte1: aaab bbcd
The a bits are unused and should not be used

The b bits determine the room's layout type, ranging from 0 to 7.

The c and d bits are unknown, but I have a feeling it's related to $AA and $A9

After that the bytes come in 3 or 2 byte object structures, used by routine $01:88E4. Objects are loaded until an object with value 0xFFFF occurs. If a value 0xFFF0 is loaded, the game will start loading Type 2 objects and will not go back to loading Type 1 objects until it is time to load the next layer. (Layer as in HM, not to be confused with the SNES' Backgrounds.) A value of 0xFFFF will also terminate the loading of Type 2 objects. The routine immediately terminates if that happens during the loading of either object type.
Type 1 Object structure: (3 bytes):

Third Byte: Routine to use. If this byte is >= 0xF8 and < 0xFC, then it is a subtype 3 object. If the index is >= FC, it is a subtype 2 object. If not, it is a subtype 1 object.

Subtype 1 Objects, first and second byte
High Byte: yyyy yycc

Low Byte: xxxx xxaa
The a bits are stored to $B2

The c bits are stored to $B4

The x and y bits are transformed into: 000y yyyy yxxx xxx0 - This is a tilemap address that indexes into $7E2000 and / or $7E4000

Use the third byte * 2 as an index into the table at $8200. This is the routine that is used to draw and otherwise handle the object. Subtype 1 objects have a maximum width and height of 4. Width and height are measured in terms of 32 x 32 pixels. (<-- last part is questionable)

Subtype 2 Objects, 1st, 2nd, & 3rd bytes:
Third Byte: ffdd dddd

Second Byte: eeee cccc

First Byte: aaaa aabb
The a bits are unused, but after all they are the marker for this type of object subtype.

The b, c, e, and f bits are transformed into a VRAM tilemap address: 000c cccf fbbe eee0

Might I add this is one messed up format? The d bits are used as an index into the table at $8470. Since such indices are going to be even, the d bits are transformed into: 0000 0000 0ddd ddd0

Subtype 3 Objects
Similar to Subtype 1, with a few small exceptions.

The vram address is calculated the same way. However, $B2 and $B4 are not used as length or width dimensions here. The routine that is used is determined as follows:

Take the original index (times two) that a Subtype 1 would have used. AND that with 0x000E. Then shift left 3 times to produce 0000 0000 0eee 0000. Then, OR in $B2 and $B4 and shift left once, so the final result is: 0000 0000 eeea abb0.

Also, this value indexes into $85F0 instead of $8200.

Type 2 Object Structure: (2 bytes)

High Byte: cccc cccc

Low Byte: bbbb ddaa
The a bits form a 2-bit value (0000 0aa0) that determines the routine to use for the object. In Hyrule Magic, corresponds to the "direction" of the door.

The b bits are transformed into 000b bbb0 and stored to $02 -> X. Corresponds to "Pos" of door objects in the Hyrule Magic. Note that these range from 0x00 to 0x16 (always even) which if you halve those values is 0 - 11 in decimal. This is easily verifiable in Hyrule Magic.

The c bits are shifted into the lower byte and stored to $04 -> A and $0A. This is later used to grab the tiles used to draw the door and the area below it. In Hyrule Magic, corresponds to "type". Note the type is 1/2 of the number listed here. This is because to avoid using an ASL A command, the c bits are always even.

The d bits are unused.

Next I'll go into the nitty gritty of the various types (the value of $04). Again note that we'll only be dealing with even values b/c that's what you'll see in the code. To convert between here [as well as the code] and Hyrule Magic, take the hex value here and divide by two. Convert to decimal and that's your Hyrule Magic "type."

Types:
0x00 - Basic door. Index = $0460

0x02 - Normal door?

0x04 - ???

0x06 - ???

0x08 - Waterfall door (only used in Swamp palace; in one room at that!)

0x0A - ???

0x0C - Trap door (probably other types but this seems to be most common)

0x12 - Adds a property to some doors allowing you to exit to the overworld (this is accomplished by writing to the tile attribute map)

0x14 - Transition to dark room?

0x16 - Toggles the target BG Link will emerge on. e.g. if Link starts on BG0 in the next room he'll be on BG1.

0x20 - Locked door specifically for BG0.

0x22 - "

0x24 - Locked door for either BG0 or BG1

0x26 - "

0x30 - Large exploded pathway resulting from a switch being pulled (unusual to have as a door as it's huge)

0x32 - Sword activated door (e.g. Agahnim's room with the curtain door you have to slash)

0x46 - warp door?

Dungeon Secrets Data

$00DB69 - $00DDE8 - Pointer Table, 2 byte local addresses, indexed by room ID.
$00DDE9 - $00E6B1 - Data

Data comes in 3 byte chunks and is terminated by an instance of $FFFF

First two bytes: A word that denotes the VRAM address that the item is found at. This identifies the item as belonging to that part of the screen.

Third byte: identifies the type of item that is hiding there. e.g. $08 is a key

Push Block Data

$0271DE-$027369 - Data

4 bytes per entry

1st word: Room that the block exists in.

2nd word: Position of the block (expressed as tilemap coordinate)

(Inter Room) Torch Data

$02736A-$027489 - Data

Consists of variable length segments consisting of:

1st word: Room that the torches belong in

After this is a series of words, each one being a tilemap address for a torch.

This list of torches is terminated by the word value 0xFFFF

Chest Contents

$00E96E - $00EB65 - Data

Array of chest information in 3 byte chunks. 168 entries in all (0xA8)

First word - Room number it is located in. MSB determines whether it is a big chest or not. (big chest if set)

Last byte - index of the type of item contained in the chest.

Entrance Data

There are $85 (Decimal: 133) normal entrances to the underworld from the overworld, and $7 (Decimal: 7) starting locations. Normal entrances and starting locations use mostly the same types of data formatted the same, however they are located in different places in the ROM. They are located and formatted thus:

Entrance Room

$014813-$01491C - Normal Entrance Data
$015B6E-$015B7B - Starting Location Data

Each entry is a 2 byte Room ID where the player is placed after using an entrance.

Scroll Edges

$01491D-$014D44 - Normal Entrance Data
$015B7C-$015BB3 - Starting Location Data

X Scroll

$014D45-$014E4E - Normal Entrance Data
$015BB4-$015BC1 - Starting Location Data

Unsure about what these do exactly. Each entry is 8 bytes long.

Format: 1 byte each. Corresponds to hyrule magic values in the "More" aka Entrance Properties dialog box.
HU -

FU -

HD -

FD -

HL -

FL -

HR -

FR -

Y Scroll

$014E4F-$014F58 - Normal Entrance Data
$015BC2-$015BCF - Starting Location Data

X Coordinate

$014F59-$015062 - Normal Entrance Data
$015BD0-$015BDD - Starting Location Data

Y Coordinate

$015063-$01516C - Normal Entrance Data
$015BDE-$015BEB - Starting Location Data

X Camera Coordinate

$01516D-$015276 - Normal Entrance Data
$015BEC-$015BF9 - Starting Location Data

Y Camera Coordinate

$015277-$015380 - Normal Entrance Data
$015BFA-$015C07 - Starting Location Data

Entrance Blockset

$015381-$015405 - Normal Entrance Data
$015C08-$015C0E - Starting Location Data

Floor Values

$015406-$01548A - Normal Entrance Data
$015C0F-$015C15 - Starting Location Data

Dungeon Values

$01548B-$01550F - Normal Entrance Data
$015C16-$015C1C - Starting Location Data

Doorway Type

$015510-$015594 - Normal Entrance Data
$015C2B-$015C31 - Starting Location Data

Ladder And BG Settings

$015595-$015619 - Normal Entrance Data
$015C1D-$015C23 - Starting Location Data

Horizontal And Vertical Scroll Properties

$01561A-$01569E - Normal Entrance Data
$015C24-$015C2A - Starting Location Data

Scroll Quadrant

$01569F-$015723 - Normal Entrance Data

Exit Door Location

$015724-$01582D - Normal Entrance Data
$015C32-$015C3F - Starting Location Data

Music

$01582E-$0158B2 - Normal Entrance Data
$015C4E-$015C54 - Starting Location Data

Entrance Values

$015C40-$015C4D - Starting Location Data

1 word each. Since the starting locations have to reference an entrance, this is necessary.

Rooms

Main Map

The main underworld map consists of $FF (decimal: 256) rooms.

@@ Line 197: / Line 197: @@
 *$015B6E-$015B7B - Starting Location Data
 <blockquote>
+Each entry is a 2 byte Room ID where the player is placed after using an entrance.
 </blockquote>
@@ Line 211: / Line 211: @@
 *$015BB4-$015BC1 - Starting Location Data
 <blockquote>
+Unsure about what these do exactly.
+Each entry is 8 bytes long.
+*Format: 1 byte each. Corresponds to hyrule magic values in the "More" aka Entrance Properties dialog box.
+**HU -
+**FU -
+**HD -
+**FD -
+**HL -
+**FL -
+**HR -
+**FR -
 </blockquote>